At present, discharge suppression of greenhouse effect gas has been globally addressed from a point of view of global warming. There is discharge suppression of carbon dioxide being the greenhouse effect gas as one of the above. Addresses relating to a power generating system such as usage of natural energy, promotion of nuclear power generation, energy saving, and making power generation efficiency higher have been made positively.
Besides, an art recovering carbon dioxide from the exhaust combustion gas using the fossil fuel occupying a major part of power generation amount has been developed as a carbon dioxide discharging method by renovation and improvement of current power generation technology. There are an absorption method using a solid absorbent, a pressure swing absorption method and a temperature swing absorption method being a derived technology of the absorption method, a thermo-alkali method using alkali metal salt solution, a membrane separation method using organic polymer having a fine pore size and an inorganic material, and so on in gas separation and purification technologies recovering carbon dioxide contained in the exhaust combustion gas. There is an amine method using a chemical absorption action of absorbent of which main ingredient is alkanolamine as a most focused method from all over the world among the above.
In the amine method, an absorbing operation making the absorbent of which main ingredient is alkanolamine absorb carbon dioxide, and a regeneration operation of the absorbent by making carbon dioxide kept in the absorbent release by performing a heat operation of the absorbent absorbing carbon dioxide are performed. It is necessary to supply heat from outside of a system for the regeneration operation of the absorbent.
A major energy required for the carbon dioxide recovery in the amine method is the heat for the regeneration operation. When the exhaust combustion gas of the fossil fuel is an object to be processed of the carbon dioxide recovery, it is often the case that combustion heat of the fossil fuel is used as a heat source for the regeneration operation of the absorbent. Accordingly, a device configuration of which heat quantity necessary for the carbon dioxide recovery is small is required.
Besides, when coals and so on are used for the fuel, sulfur oxide, particulates, and so on are mixed in the exhaust combustion gas. The sulfur oxide, the particulates, and so on are usually removed by a removing process, but remaining minute amounts of minor components of these sulfur oxide, particulates, and so on are accumulated in the absorbent, and there is a possibility in which influences such as stains of a heat exchanger and a transportation machine (for example, pumps), and a change in absorbent characteristics occur. Besides, there is a possibility in which a deterioration product of the absorbent and a corrosion product of structural materials may have similar effects. Accordingly, the above-stated impurities (minor components) accumulated in the absorbent are necessary to be removed immediately. Besides, it becomes necessary to establish an art of which loss of the absorbent and heat loss in accordance with the removal are small.
A method in which a filtration membrane apparatus is provided in a carbon dioxide recovery system, a vaporizer heating and concentrating impurity containing solution collected by the filtration membrane apparatus is disposed to remove solids accumulated in the absorbent of the carbon dioxide recovery system (JP-A 2008-207123 (KOKAI)), and a method in which an anion exchange resin tower is provided inside a carbon dioxide recovery system, a solid-liquid separator is disposed at a previous stage thereof to remove solids and anion impurities in the absorbent (JP-A 2008-238113 (KOKAI)) are proposed to solve the above-stated problems.
An operation in the filtration membrane apparatus is not clearly described in JP-A 2008-207123 (KOKAI), and there is a possibility that heat energy held by the absorbent to be a high temperature of 100° C. or more discharged from a regeneration tower may be lost. Besides, there is no description relating to a filtration membrane material used under the high temperature environment, and there is a possibility in which impurities are eluted into the absorbent by an eluting material from the membrane material depending on a selected material.
The method in which ionic impurities are removed by the anion exchange resin is described in JP-A 2008-238113 (KOKAI). However, it is known that cation impurities derived from an anion exchange group having an amino group is eluted resulting from deterioration in an ion exchange group of an ion exchange resin. Accordingly, a countermeasure for the cation impurities is normally taken at a subsequent stage of the anion exchange resin by a cation exchange resin and so on, but there is a problem in an operation under the absorbent to be an alkali environment containing high concentration alkanolamine.
Further, the anion exchange resin tower is provided to remove organic acid resulting from an oxidized deterioration product of alkanolamine in JP-A 2008-238113 (KOKAI), but the ion exchange group held by the anion exchange resin is known to have low heat resistance and oxidation deterioration resistance. Accordingly, there is a problem that the elution of cation occurs from the anion exchange group having amino group, and the impurities in the absorbent increase if the anion exchange resin is used under the environment in which alkanolamine is oxidized and deteriorated. Besides, there is a possibility in which the heat loss occurs caused by the stains of the equipments such as the heat exchanger disposed on a circulation path of the absorbent resulting from the impurities. An object of the present embodiments is to provide a carbon dioxide recovery system suppressing the heat loss.
A carbon dioxide recovery system according to the present invention includes: an absorber bringing exhaust gas containing carbon dioxide into contact with absorbent reversibly absorbing or releasing carbon dioxide at above or below a predetermined temperature, and making the absorbent absorb carbon dioxide in the exhaust gas; a regenerator releasing carbon dioxide in the absorbent by heating the absorbent absorbing carbon dioxide at the absorber; a reflux pipeline flowing back the absorbent regenerated at the regenerator to the absorber; and a filter introducing at least a part of the absorbent, removing solids accumulated in the introduced absorbent, and returning the absorbent after the solids are removed to a vicinity of a portion where the absorbent is introduced.
The filter is made up of a separation membrane made of a fluorocarbon resin, or made up of a material in which filter media in fine particle states are held by a mesh.
A material made of nickel group alloy is suitable for the filter media in the fine particle states and the mesh.
When the filter in which the filter media in the fine particle states are held by the mesh is made up of the nickel group alloy, a specific gravity of the filter media becomes heavier than the solids supplemented from the absorbent, and therefore, it is possible to repeatedly use the filter media by separating the filter media and the supplemented solids by a specific gravity difference, collecting the filter media, and introducing them into the filter again when the filter is back-washed.